In accordance with the Philosophy of Tiddlers, documentation tiddlers are typically short and interlinked.
When a tiddler seems as if it needs to contain subheadings, this is often a sign that it should in fact be split into several tiddlers. But it is reasonable for a reference tiddler to consist of an untitled introductory section followed by a titled section of details.
Consistency of terminology is essential if the reader is not to become confused. Consistent typography and punctuation lend a professional quality to the documentation. Macros can improve the consistency and maintainability of the text.
Use numbered lists for step-by-step instructions, and bullet points for lists whose order is arbitrary. Use a definition list in preference to a bulleted list if each bulleted item would begin with a term and a colon. If at all possible, avoid burdening the reader with a nested list.
Use a table when information naturally falls into three or more columns, and also for lists of parameters, attributes, etc in reference tiddlers.
Avoid periods at the end of list items, headings and table cell text.
The documentation describes the current reality of TiddlyWiki. Avoid discussing future aspirations.